Effects of intrinsic degrees of freedom in enhancement of sub-barrier fusion excitation function data and energy-dependent one-dimensional barrier penetration model

Abstract

We have analyzed the role of barrier modification effects (barrier height, barrier position, barrier curvature) introduced due to the energy-dependent Woods-Saxon potential model (EDWSP model) and the coupled channel model on the sub-barrier fusion dynamics of 32;36 16 S þ 90;96 40 Zr reactions. The influence of inelastic surface excitations of colliding pairs and multi-neutron transfer channels is found to be a dominant mode of couplings. The coupling of relative motion of colliding nuclei to these dominant intrinsic degrees of freedom leads to a substantially large fusion enhancement at belowbarrier energies over the expectations of one-dimensional barrier penetration model. The coupled channel calculations based upon static Woods-Saxon potential must include the internal nuclear structure degrees of freedom of colliding nuclei for complete description of experimental data. On the other hand, theoretical calculations based upon the EDWSP model along with Wong formula provide a complete description of sub-barrier fusion enhancement of various heavy-ion fusion reactions. In EDWSP model calculations, significantly larger values of diffuseness parameter ranging from a = 0.98 fm to a = 0.85 fm are required to address the observed sub-barrier fusion enhancement of 32;36 16 S þ 90;96 40 Zr reactions. Furthermore, within the context of EDWSP model, it is possible to achieve an agreement with the experimental fusion crosssectional data within 10 %. For four heavy-ion fusion reactions, only at 4 fusion data points out of 90 fusion data points deviates exceeding 5 %, while 86 fusion data points lie within 5 % and hence the EDWSP model is able to account the above-barrier portion of the fusion cross-sectional data within 5 % with a probability greater than 90 %.

Comprehensive analysis of heavy-ion fusion reactions around the Coulomb barrier

“…In heavy ion fusion dynamics, it has been experimentally observed that the fusion excitation functions for the large number of projectile-target combinations were found to be enhanced over the outcomes made via onedimensional barrier penetration model (1-DBPM) and is one of the most common problems in the heavy-ion interactions. This anomalous behaviour of fusion excitation function introduces the importance of multidimensional tunneling [1][2][3][4][5][6][7][8][9][10][11][12][13]. In literature, it has been well established that the nuclear structure degrees of freedom associated with reaction partners such as low-lying surface vibrations, zero-point motion, neck formation, static nuclear deformation, entrance channel mass asymmetry, rotational states and/or nucleon transfer channels affect the fusion process and played an important role to establish favourable conditions for the synthesis of a particular compound nucleus [13][14][15][16][17][18][19][20][21][22].…”